Tissue Engineered Approaches to the Treatment of Chondral Lesions: Clinical Experience

TISSUE ENGINEERED APPROACHES TO THE TREATMENT OF AHLBACK STAGE I-II KNEE OSTEOARTHRITIS: CLINICAL EXPERIENCE WITH HYALOGRAFT-C AND UNLOADING OSTEOTOMY

STEFANO ZANASI

POLICLINICO DI MONZA

UNITA’ OPERATIVA DI ORTOPEDIA E TRAUMATOLOGIA

RESPONSABILE: DR. STEFANO ZANASI

e-mail:

INTRODUCTION

Gonarthritis is due to altered distribution of stresses at the knee: the beared stresses go beyond the biological joint resistence.

Varus alignment is the most common alignment in OA: up to 75% of all patients have it. In term of cartilage degradation of the tibio-femoral compartments, the medial side is usually the worst affected although patello-femoral arthritis is frequently accompanied. Subjects with varus knee alignment are bowlegged and have negative hip-knee-ankle angles: the condition is common and does not impose functional restraints unless the varus is severe. Progressively this condition causes knee instability and subluxation, expecially if the ACL is lax. Subluxation is common in oblique knee condition in which the joint surfaces have an exaggerated lateral to medial downward tilt: an arthritic disease pattern of joint involvement is related to alignment through cause or effect both. The frequent patellar malalignment in OA probably indicates that the long bones have torsional abnormality at the level of the patello-femoral mechanism: lateral displacement of patella in the varus condition have seen in about 30% of patients (Harrison MM et AA Clin Orthop 1994-309: 53-56).

Valgus alignment deformity is less common than varus pattern: it often arise from disease like renal rickets, polyostotic fibrous dysplasia, developmental displasias and rheumatoid arthritis and is seen more often in women than in men. Correctional osteotomies for valgus abnormalities should be made whenever is possible at the centers of rotational alignment. Subjects with valgus alignment are knock-kneed and have positive HKA angles. The Q angle is greater than normal and vector forces acting on the patella predispose it to sublux laterally. Initial enthusiasm for using a proximal tibial varus osteotomy to correct a valgus deformity of the knee waned after data showed that the results of this operation were often unsatisfactory (Shoij h. et AA J B J S Am 55:963-973,1973). This procedure will allow the postponement of joint replacement surgery in the high-demand patient while not adversely affecting the technical demands or clinical results of a later TKA.

Proximal tibial valgus osteotomy (HTO) has proven to be an effective operation for medial compartment OA in the young patient who is of too high demand by reason of age, size, occupation, or lifestyle for unicompartmental or TKA.

After unloading high tibial osteotomy the ratio of bone mineral density of the medial femoral condyle to the lateral femoral condyle decreases sharply within one year according to Pauwels law (bone quantity is directly linked to the size of applicated forces) (Akamatsu Y et AA Clin Orthop 1997 Jan 334:207-214). Aim of the unloading osteotomy is to redistribute the loading forces bringing them under the limits of joint tolerability: best results have been obtained when anatomical axis is from 5to 15° valgus (Yasuda K et AA Clin Orthop 1992 282:186-195), but correction amount should be not too important or must be at the 62% of the tibial external plate.

Although the incidence of proximal valgus osteotomy for OA has decreased because of advances in total knee arthroplasty, there is still a need for this operation in the young high-demand patient with medial compartment OA.

A success rate of 82% HTO alone was reported in patients under the age of 60 who wished to participate in vigourous sport or work activities (running, jumping. etc) (Nagel A t AeA, JBJS Am 78:1353-1358, 1996). Other reports in the literature have yielded success rates from 60% to 70% at 10 years for HTO alone.

HTO with additional Pridie drilling or abrasioartroplasty associated with continuous passive motion showed cartilage regeneration thicker and more stable, sometimes covering all of the preexisting erosions in confront of groups without additional operative arthroscopy (Schultz et AA Knee surg Sport Traumat Arthrosc 1997 7(1):29-36). In addition HTO with artroscopic abrasion arthroplasty promotesfibro-cartilage regeneration in osteoarthritic knee with eburnation (Akizuki S. et AA Arthroscopy 1997 Feb 13(1), 9-17). But overall Maynou c (et AA Acta Orthop Belg 1998 Jun 64(2):193-200) stresses that concomitant correction by HTO allows to relieve stresses from the chondral grafts and Tom Minas underlines that “complex and salvage treatment cases having adjuvant treatment including valgus tibial (n=24) or tibial tubercle (N=15) osteotomies at the 2 ys f.up show statistically significant functional improvements with patients satisfaction at 24 ms. for simple, complex and salvage categories of 60%, 70% and 90% respectively (Clin Orthop 2001 Oct (391 suppl) S349-361)

Cartilage has limited self-repair capabilities and articular cartilage defects will ultimately result in chronic tissue losses. To contrast this relentless outcome new reconstructive techniques have been developed such as autologous cultured chondrocyte implantation whose medium-term results are encouraging but with limitations like problematic handling of cultures in suspension, complicated surgical procedure, chondrocyte de-differentation (cells acquire a fibroblastoid phenotype and loose the capacity to produce the typical ECM molecules able to regenerate a physiological-like tissue). Hyaluran-based tissue engineering by the use of biomaterials derived from jaluronic acid (Hyaff-11) realizes an ideal three-dimensional scaffold for the cultivation of human autologous chondrocytes that is able to restore the differentiated phenotype maintaining chondrocyte capability to produce collagen type II (hyaline cartilage marker) by associating an improved and simplified implant technique. The bio-engineered tissue due to its 3D structural an physical properties very closed to the lost cartilage realizes an optimal filling of the tissue gap, stable on large defects, with resurfacing of complete articular surfaces: in these cases unloading/corrective osteotomy is usually concurrently associated. Tibio-femoral, patello-femoral malalignment, as well ACL insufficiency or bone insufficiency (ostheocondritis dissecans, avascular necrosis, ostheochondral fractures) must be managed prior to, or concurrently managed with the chondral injury.

According to Tom Minas treatment classification (Am. J. Knee Surg. 2000; 13(1):41) ICA represent the gold standard for SIMPLE cases in healthy knee with unipolar isolated lesion to the weight bearing femoral condyles and no other surface exhibiting greater than Outerbridge grade I or II chondromalacia. In COMPLEX cases for single extensive/massive unipolar chondral defect or multifocal lesions of the femoral condyles, tibial plateau, trochlea or patella, concurrently with concomitant realignment procedures or ACL reconstruction or prior to staged bone graft, ACI represents as well as in coin lesions, the fist line of treatment able to restore a durable neo-reonstructed hyaline-like cartilage with satisfactory results in over 85% of cases of condyle and troclea defects and in 65% of tibial and patellar defects. With different clinical expectations and prognosis SALVAGE procedures are performed for posttraumatic or degenerative osteoarthritis Ahlback stage 0 or stage I (joint space narrowing lesser than 50%) or kissing lesions in generalized chondromalacia greater than Outerbridge grade II: ICA is performed concurrently with realignment procedure and ACL reconstruction and prior to bone grafting. In these patients younger than 55-58 years-old who want to avoid, or better to delay, TKA and strongly require, as alternative, resurfacing, we have obtained extremely promising results.

PREOPERATIVE PLANNING AND 1ST ARTROSCOPICAL PROCEDURE

The Hyalograft-C ACI protocol requires clinical examination (anamnesis), X-Rays in orthostatism and assial X-Rays of patella, NMR and arthroscopy.

Cartilage biopsy of 150 mg is arthroscopically taken from a nonbearing area (notch-plasty). Chondrocytes are culturedin vitro and on 14th day seeded on Hyaff scaffold for cartilage formation into two weeks

SURGICAL TECHNIQUE

A. High valgus osteotomy according to Puddu:the plates present two serie of holes, one proximal for two cancellous AO screws and one distal for two cortical AO screws; a different thickness tooth from 5 to 15 mm (5-7,5-10-12,5-15mm): aim of the plate is the osteotomy syntesis; aim of the tooth is to avoid the bone collapse with related lack of the established correction

Le placche hanno due fori ,uno prossimale ed uno distale,per una vite AO da spongiosa (prossimale) ed una vite AO da corticale (distale); ed hanno un dente di vario spessore da 5mm a 15 mm;la profondità del dente è uguale per tutti ed è di 4mm. Scopo della placca è la sintesi dell'osteotomia mentre il dente deve prevenire il possibile collasso dell'osso con la conseguente perdita della correzione voluta. L'unico strumento accessorio è una forchetta graduata a cuneo che ,introdotta nell'osteotomia,e spinta a colpi di mazzuolo deve aprire il cuneo per i mm decisi preoperatoriamente sull'esame radiografico.Il focolaio osteotomico viene mantenuto aperto e la placca viene introdotta nello strumento a forchetta. Una volta che la placca è inserita si controlla in amplificatore la correzione ottenuta e si passa alla sintesi ed all'applicazione del trapianto osseo di cresta iliaca se l'osteotomia è da 7,5 a 15mm,mentre se l'osteotomia è di 5 o 7,5mm è sufficiente utilizzare dell'osso prelevato dalla tibia distalmente alla osteotomia stessa. Incidiamo cute e sotto cute fino ad arrivare ai tendini della zampa d'oca con una incisione longitudinale mediana da 12-14 cm.Quindi sezioniamo a tutto spessore,trasversalmente,il fascio superficiale del legamento collaterale interno,che sarà lasciato aperto anche a fine intervento.I tendini della zampa d'oca vengono dissecati e caricati distalmente,quindi con uno scollaperiostio si libera la tibia e a questo punto i vasi vengono protetti da un divaricatore introdotto postero medialmente.Sotto controllo fluoroscopico si introduce un chiodo di Steinmann che parte a circa 4cm dal piatto tibiale interno e si dirige obliquamente e prossimalmente fino ad arrivare ad 1cm circa al di sotto del margine esterno del piatto tibiale esterno. Non è mai necessaria una osteotomia di perone. Quando il chiodo è nella posizione desiderata,con la sega e con l'osteotomo si esegue l'osteotomia tibiale fino ad arrivare a circa 5mm dal margine esterno della metafisi tibiale.Tale tessuto osseo servirà da cerniera ed in associazione alla placca garantirà la stabilità dell'osteotomia.Quindi valgizzando il ginocchio si esegue la clasia della corticale esterna e l'apertura del focolaio osteotomico ove viene introdotto lo strumento divaricatore a forchetta graduato.Battendo su questo strumento l'osteotomia viene aperta fino alla misura decisa e a questo punto si introduce la placca con il dente adatto. Sotto amplificatore di brillanza e con un filo metallico si cercano i reperi:testa del femore- centro della cavilgia e si controlla dove passa il filo metallico nell'articolazione del ginocchio.Il filo metallico dovrebbe essere esterno al profilo rotuleo in antero-posteriore o passare esattamente nel punto del piatto tibiale esterno scelto dall'operatore sulle radiografie sotto carico. Quindi si passa alla sintesi con due viti AO ,una da spongiosa prossimale e da corticale distale.Una volta certi della qualità della sintesi il focolaio viene riempito con attenzione di osso autologo tibiale o con LUBBOCK a seconda del dente utilizzato.Il collaterale interno viene lasciato aperto in quanto essendo il fascio superficiale e non il profondo non arreca alcun danno alla stabilità del ginocchio

B. Surgical procedure by mid line standard arthrotomy is performed at 60 days. After lesion curettage (abrasion) by a simple curette or a low power burring of the back of the lesion we proceed to realize a net cut of the edge of the lesion up to the normal cartilage tissue. Then, if the bed is sclerotic we perform drilling in order to decrease the high local pressure to relieve pain and to allow a good uptake. Naturally it could be said that stem cells from the bone marrow could colonize with fibroblasts, but in the saples we have taken after the 2nd look arthroscopy we never verified a mixed population of the cartilage like fibro-cartilagineous tissue.

The Hyalograft-C patchesare gently pushed in the lesion and trimmed if needed to match the shape of the defect: when the lesion is contained but wide I resort to resorbable 4-0 stay sutures. If the lesion is uncontained I resort to resorbable microanchors to fix the graft in order to avoid the sliding and removal during motion.

Postsurgical treatment consists of articular drainage in an area far from the graft, and compressive bandage for 24 hours postgrafting. Articular movement is forbidden for 24 hours starting with passive rehabilitation with CPM from the 2nd day postop. concurrently with isometric exercises for quadriceps muscles. Articular weight-bearing may be applied from the 5th week postop and gradually brought to normal activity at 12-20 weeks. Control visit are performed at 1,3,6,12,18 months from surgery. NMR is performed at 3 and 6ms postop; arthroscopic second look with biopsy for hystological tissue typization is performed at 12 monts postop.

Patients and Methods

94 of 187 patients treated from May 1999 to June 2002 for chondral defects Outerbridge III/IV have been followed: 46 out of 94 were complex or salvage procedure according to Tom Minas classification.

Complex procedures (30 cases) include: massive unipolar shouldered defects of the lateral condyle (13 cases), and massive unipolar medial condyle defects plus lateral condyle or troclea coin lesion (15 cases) that have concurrently respectively managed by low varus femoral osteotomy and by high valgus osteotomy; plurifocal coin defects ( 2 cases).

Salvage procedures (16 cases) include: 3 cases of limited and shouldered coin kissing lesions not requiring realignment procedures(<50% emi-joint rime), 12 cases of unicompartmental O-A and unshouldered kissing lesions and 1 case of aseptic osteonecrosis of medial femoral condyle that have been concurrently managed with filling by Norian and unloading corrective osteotomy. In particular 61% 28/46) of these cases, that is 30 % of the whole cases serie (28/94) have been concurrently managed by unloading osteotomy according to Puddu technique. The overall population was between 27 and 56 years old (average 42 years old), 57% female, with an average size of the defect of 12 cm2 (range 7.5 – 32 cm2)

28/94 patients who had been treated with HTO and Hyalograft C for cartilage lesions of the knee have been reviewed retrospectively; the results of the functional outcome were prospectively obtained. Being this investigation observational and voluntary in nature, no inclusion or exclusion criteria have been applied. However, participating surgeons were encouraged to primarily include patients with a follow-up time from Hyalograft C implantation of at least 12 months.Data collection was based on a Case Report Form which has been designed taking into account the most recent guidelines of the International Cartilage Repair Society (ICRS) discussed at the 3rd ICRS meeting of April 28, 2000 in Gotheborg (21).The average follow-up time for this series of patients was 19 months (range 12-47). They were 12 males and 16 females, with a mean age of 41.4 years (range 34-55) affected by chondral defects of the knee caused by trauma (34.6 %), osteochondritis dissecans (11.8 %) and lesions that were degenerative and/or microtraumatic in nature (53.6 %). 76.6.% of the subjects had a single lesion, and the remaining 23.4% multiple lesions, corresponding to a total number of defects of 138, averaging 1.2 defects per patient. As expected, the vast majority of the defects were localized on condyle (74.6%): primarily on the medial femoral condyle (63.8%), the remaining on the lateral condyle. The remainder of the defects was localized on the throclea (8.7%), patella (8.7%), and tibial plateau (8.0%). The defects treated were graded Outerbridge IV in the vast majority of cases (85.4%) and grade III in the remaining percentage. The mean surface area implanted per patient was 3.42 cm2 (SD=2.57) ranging from 0.75 to 12.25 cm2.More than half of the patients (53.2 %) had undergone previous surgery on the affected knee. Remarkably, 36% of the total population had been previously subjected to cartilage surgery, including debridement and bone marrow stimulation techniques, which eventually proved unsuccessful. 29.7% of patients had underwent previous meniscus and/or ligament surgery. 28% of patients underwent one or more associated surgical procedures at the time of Hyalograft® C grafting. These included high tibial valgus osteotomy and/or patellar realignment osteotomy (in 7.2% of the population) and meniscus and/or ligament surgery (24.3%).

Hyalograft® C was implanted without any coverage or fixation system in 58.6% of the cases, whilst fibrin glue and/or sutures were used in 34.2 % of the cases. The functional outcome was obtained using 4 endpoints: patient’s subjective evaluation of knee conditions and quality of life, surgeon’s knee functional test, arthroscopic evaluation of cartilage repair and histological assessment of the grafted site.

Patients were asked for a subjective evaluation of the knee symptoms and physical function using the IKDC Subjective Knee Evaluation Form (21), and for their quality of life using the EuroQol EQ-5D questionnaire (22). Baseline data were obtained by asking patients to answer these questionnaires retrospectively for the conditions of their knee and their quality of life after injury but just before Hyalograft® C implantation.Knee functional outcome was obtained by the surgeon according to the IKDC objective knee examination form (21).Thirty-seven patients underwent second-look arthroscopy, performed as a consequence of an adverse event in four cases and for investigative purposes subsequent to patient’s consent in the remaining cases. Quality of the repair tissue was classified according to the integration of the graft into the surrounding cartilage (0–4 points), the degree of defect fill (0–4 points), and the macroscopic appearance (0–4 points), giving the best possible defect-repair score of 12 points (6).Twenty-four patients out of the 37 who underwent second-look arthroscopy consented for a biopsy harvesting in the area of graft implantation. Samples were analyzed by two independent, blinded investigators, who rated regenerated cartilage as hyaline-like, fibrocartilage or mixed tissue based on criteria of cellularity, cell distribution, matrix composition and collagen type I and II immunolocalization. Finally, the occurrence of adverse events in the post-op period was recorded.The entire set of data was included in a unique database. Statistical analysis was performed using the SAS system statistical software package (SAS Institute, Cary, North Carolina, USA).An one year MRI scan, video arthroscopy and biopsy of the repair have been made

Results

Patient’s assessment of knee conditions and quality of life (N=28). 92.7% of the patients experienced a subjective improvement in knee function and symptoms. Only 7 patients (6.4 %) resulted having a worsening of their knee conditions at the follow-up control with respect to pre-surgery status.The mean subjective IKDC score obtained was 36.8 (SD = 12.1) at baseline and 73.1 (SD = 21.3) at the follow-up control. The difference proved statistically significant (P<0.0001, Student’s t-test, Fig. 1A).89.9% of patients experienced an improvement in their quality of life, as assessed by the EQ-VAS. The situation was found to be unchanged in 6 patients and worsened in 5 patients (4 of them experienced a worsening also in the subjective knee evaluation scores).The difference in the mean EQ-VAS score (Fig. 1B), which changed from 61.0 (SD = 16.7) to 84.3 (SD = 17.1) was statistically significant (P< 0.0001, Student’s t-test).As expected, the majority of the improvements was related to mobility (63 % of patients improved), usual activities (68 %) and reduced pain/discomfort (83 %).When the IKDC subjective outcome was analysed in function of lesion size and time from Hyalograft C implantation, a positive trend of subjective improvement has been observed with increasing size and follow-up times (Fig. 2 A and B). Clinical symptoms (pain, lock, swelling, full/partial giving way) significantly decreased within the 3rd month, and completely ceased, in all cases, within 6 months with good functional recovery and significative improvement of ROM (flex-ext >15%) with average pre-op. active ROM of 110° (range 80° - 140°) and average post-op active ROM of 130° (range 110° - 140°). We verified satisfactory clinical results at 18 ms average f.up : best functional results in high valgus osteotomy (26/46) vs. low varus osteotomy (2/46). As reported in other serie.(Maynou C. et AA Acta Orthop Belg 1998 Jun; 64(2): 193-200) concomitant correction by high tibial osteotomy allows to relieve stresses from the chondral grafts. Complex and salvage treatment cases having adjuvant treatment as valgus tibial or varus femoral osteotomies at the 18 ms. f.up. showed statistically functional improvements. Patients satisfaction at 24 ms. for complex and salvage procedures –as Minas cases serie - is about 75% and 90% respectively. The results for all patients with greater 12 ms. follow up are aggregate scores for the overall group. Although these results demonstrate marked clinical and statistical significance, the outcome are clearly superior for the healthy knees ( complex cases) when separated from the knees with evidence of ostheoarthritis (salvage). Although the salvage cases also significantly are improved, the sample size is too small. Surgeon’s knee examination (N=28) :Figure 3 shows the distribution of percent of patients displaying the four possible IKDC knee group grades. At follow-up, final grade was normal in 59.0% of patients and nearly normal in 31.1%, resulting in a proportion of 90.1% of patients displaying knee conditions within the two best categories. Only in one case the knee was rated as severely abnormal: this may have been related to the occurrence of a marked fibroarthrosis.Macroscopic assessment of the repair tissue (N=17). The mean repair score for this set of patients, at a mean arthroscopy time from surgery of 12.2 months, was 10.7 (range 3–12). Cartilage repair was found to be normal in 43.2% of the cases, and nearly normal in 54.1% (20 cases, 9 of which scored 11). Thus, in 36 cases the cartilage repair was rated as biologically acceptable. Only one case, associated to periosteal hypertrophy, was rated as severely abnormal, having a biologically unacceptable appearance with significant fissuring of the repair tissue and no integration with the surrounding cartilage. Biopsy analysis (N=24).The majority of the biopsies (n =15/24) were rated as hyaline-like, five cases as mixed tissue and four as fibrocartilage. Average second-look arthroscopy time post-surgery for this subset of patients was 14.2 months. During second-look arthroscopy, in the first 19 cases, a cartilage biopsy has been obtained from the center of the repaired defect, 12 months after grafting: the arthroscopical views showed total scaffold biodegradation, a significantly improved appearance of the tissue and uniform cartilagineous resurfacing with good mechanical resistance to probe palpation, although cartilage fibrillation and areas of uneven cartilage stiffness were visible in almost of the cases. The morphological analysis of the newly formed cartilage tissue revealed an heterogeneity throughout the repaired tissue: high proteoglycan content, limited presence of collagen type I and abundant expression of collagen type II, a typical component of hyaline extracellular matrix. The only two third look arthroscopy at 31ms. f.up completely confirmed the features of the hyaline cartilage. Further work is required on the histological examination of patients treated with Hyalograft C at longer time points (3 and 5 years) in order to appreciate the quality of the reconstructed tissue and the maintenance of the cartilage quality.