OSTEOCHONDRAL ALLOGRAFT TRANSPLANTATION for the KNEE: POST-OPERATIVE REHABILITATION

Lesion Size Location Dependency on Maximum Pressure in Osteochondral Defects: Experiments and Finite-Element Analysis

Background

Osteochondral defects (OCDs) in the knee joint have significant clinical implications, particularly regarding contact pressures and pressure distribution. Understanding how these factors are influenced by defect size and location is crucial for developing effective therapeutic strategies.

Purpose/Hypothesis

The purpose of this study was to investigate the impact of defect size and location on contact pressures and pressure distribution in the knee joint. It was hypothesized that an increase in defect size would result in elevated contact pressures and alterations in pressure distribution, with specific variations related to defect location.

Study Design

Descriptive laboratory study.

Methods

The study utilized 6 cadaveric knees, including the patella and fibula, subjected to controlled compressive loading for measuring contact pressures. Simultaneously, computed tomography-based models were created for finite-element analysis (FEA) to investigate the impact of varying defect sizes and locations on contact pressures and pressure distribution in the knee joint, excluding the patellofemoral joint. The study employed analysis of variance to assess contact pressure and defect size association. Comparison between medial and lateral femoral condyles at full extension and 30° flexion angle was performed, followed by post hoc testing. Fisher exact test analyzed peak pressure point location and defect size, categorizing them into medial and lateral.

Results

An increase in defect size corresponded with heightened contact pressures on both medial and lateral femoral condyles at full extension (P = .013 for medial and P = .024 for lateral). However, this correlation did not yield significant differences at 30° of flexion (P = .674 for medial and P = .333 for lateral). During mechanical testing, the highest pressures occurred near 5 mm defect dimensions. FEAs showed a significant increase in pressure and circumferential-edge stress with 7-mm defects. Peak contact pressure points shifted laterally with more significant defects.

Conclusion

Our study demonstrated the impact of defect size, location, and alignment on knee joint contact pressures. Intervening promptly with defects exceeding 3 mm is crucial, as significant stress levels manifest beyond this threshold. Significant increases in contact pressures were noted with larger defect sizes, particularly between 3 and 10 mm at full extension. Peak pressure points shifted with defect size increments, and alignment variations showed minimal stress variation at 30° compared with 0°. FEA validated increasing contact pressures up to 7 mm defect size, beyond which pressures stabilized or slightly decreased. A concentrated pressure distribution on the medial side was observed. These findings inform our understanding of the biomechanical implications of OCDs.

Clinical Relevance

In the field of sports medicine, this research offers valuable insights to clinicians and researchers, elucidating key factors influencing knee joint health and the potential consequences of OCDs.

Comparison of Patient-Reported Outcomes for Immediate Unrestricted Weightbearing Versus Restricted Rehabilitation Protocols After Osteochondral Allograft Transplantation to the Distal Femur

Background

There is no standardized rehabilitation protocol after osteochondral allograft (OCA) transplantation surgery to the distal femur. The spectrum of recommendations includes restrictions to toe-touch weightbearing (TTWB) for 6 weeks and immediate weightbearing as tolerated (WBAT).

Purpose/Hypothesis

The purpose of this study was to compare outcomes for immediate unrestricted WBAT to restricted TTWB after OCA transplantation to the distal femur. It was hypothesized that the immediate WBAT protocol would be noninferior to delayed, restricted TTWB.

Study Design

Retrospective cohort study.

Methods

A total of 74 patients who underwent press-fit, dowel technique OCA transplantation to the femoral condyle(s) for contained (International Cartilage Repair Society grade 3-4) lesions were identified in the Metrics of Osteochondral Allograft multicenter database: 36 patients (18 women/18 men) who were prescribed TTWB were allocated to the control cohort and 38 patients (21 women/17 men) who were prescribed WBAT were allocated to the test cohort. Baseline characteristics were similar except for larger grafts in test patients (3.4 vs 2.7 cm2; P = .004) and higher body mass index (BMI) in control patients (27.8 vs 24.9 kg/m2; P = .01). Failure rates, final patient-reported outcome (PRO) scores, and PRO score changes from baseline were compared between the cohorts. Multiple regression was used to control for potential confounders and investigate noninferiority using minimal clinically important differences (MCIDs).

Results

The mean follow-up was 2 years (range, 1-5 years) in both cohorts. Both cohorts showed significant improvement in all PRO scores, with no significant between-group differences in failure rates, final PRO scores, or PRO changes from baseline. There were 3 cases of failure in each cohort (control cohort: allograft revision [n = 2], debridement [n = 1]; test cohort: chondroplasty [n = 2], conversion to total knee arthroplasty [n = 1]). Regression analysis showed that adjusted differences in final PRO scores based on weightbearing protocol were minor and less than MCIDs when controlling for age, sex, graft size, BMI, and allograft location. Analysis of the MCIDs with respect to the lower bounds of the confidence intervals indicated that WBAT was noninferior to TTWB with a reasonable degree of confidence (range, 84.1%-99.9% confidence).

Conclusion

Results indicated that immediate unrestricted WBAT after OCA transplantation to the distal femur was equally safe and effective compared to restricted TTWB.

Arthroscopic Measurements Predict Knee Chondral Lesion Size More Accurately Than Magnetic Resonance Imaging, and Mechanism of Injury Influences Ability of Either Technique to Predict Graft Size

Purpose

To compare osteochondral defect size measurements and characteristics across magnetic resonance imaging (MRI) and arthroscopy and at the time of osteochondral allograft (OCA) transplantation or autologous chondrocyte implantation (ACI).

Methods

Patients who underwent ACI and OCA transplantation at a single institution between 2015 and 2019 were retrospectively identified. Patients were excluded if they had severe osteoarthritis, MRI scans were not available for review, surgical records did not include defect sizing necessary for analysis, or operative reports were not available. Osteochondral lesion characteristics including size were collected preoperatively by MRI and arthroscopy and at the time of definitive open surgical intervention. Subgroup analysis was performed comparing measurement techniques depending on the corrective surgical approach used, as well as depending on the mechanism of chondral injury, to determine whether these factors had any effect on the ability of arthroscopy or MRI to predict graft size.

Results

Overall, 136 chondral lesions were addressed, with restoration procedures in 117 patients (mean age, 32.5 years). The average difference between the final graft size and the lesion area measured with index arthroscopy was 116 mm2, whereas the average difference between the final graft size and the lesion size measured with preoperative MRI was 182 mm2 (P < .001). Depending on surgical technique, measurements with MRI were more similar to the final graft size when a patient underwent OCA transplantation versus ACI (P = .007). Depending on the mechanism of injury, MRI measurements of lesions were closer to the graft area when lesions resulted from trauma (P = .047).

Conclusions

Chondral lesion size as determined by preoperative MRI is less accurate than arthroscopic measurement. The mechanism of injury leading to chondral damage and degree of damage may influence the ability of MRI and arthroscopy to accurately measure chondral lesions and predict the final graft size used in surgical correction.

Level of Evidence

Level III, retrospective cohort study.

Bulk Osteochondral Allograft for a Firearm Injury to the Medial Femoral Condyle in a Military Service Member: A Case Report

A 27-year-old U.S. military active duty male sustained an accidental, self-inflicted left knee gunshot injury with an unsalvageable medial femoral condyle injury. The patient underwent bulk osteochondral allograft transplantation. Nine months post-operation, the patient was fit for full military duties with no reported functional limitations and remained on active duty. Severe knee medial femoral condyle bone loss after accidental firearm injury is uncommon. Bulk knee osteochondral allograft transplantation to the medial femoral condyle provided a successful treatment option for an active duty U.S. military member with multicompartment osteochondral defects and severe medial femoral condyle bone loss due to a gunshot injury.

Characterizing Osteochondral Allograft Biomechanics for Optimizing Transplant Success: A Systematic Review

Osteochondral allograft (OCA) transplantation has been largely successful in treating symptomatic articular cartilage lesions; however, treatment failures persist. While OCA biomechanics have been consistently cited as mechanisms of treatment failure, the relationships among mechanical and biological variables that contribute to success after OCA transplantation have yet to be fully characterized. The purpose of this systematic review was to synthesize the clinically relevant peer-reviewed evidence targeting the biomechanics of OCAs and the impact on graft integration and functional survival toward developing and implementing strategies for improving patient outcomes. The Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, Cumulative Index to Nursing and Allied Health (CINAHL), Google Scholar, and EMBASE were searched to identify articles for systematic review. This review of relevant peer-reviewed literature provided evidence that the biomechanics related to OCA transplantation in the knee have direct and indirect effects on functional graft survival and patient outcomes. The evidence suggests that biomechanical variables can be optimized further to enhance benefits and mitigate detrimental effects. Each of these modifiable variables should be considered regarding indications, patient selection criteria, graft preservation methodology, graft preparation, transplantation, fixation techniques, and prescribed postoperative restriction and rehabilitation protocols. Criteria, methods, techniques, and protocols should target OCA quality (chondrocyte viability, extracellular matrix integrity, material properties), favorable patient and joint characteristics, rigid fixation with protected loading, and innovative ways to foster rapid and complete OCA cartilage and bone integration to optimize outcomes for OCA transplant patients.

Effects of Patient Assessment and Education by an Integrated Care Team on Postoperative Adherence and Failure Rates After Osteochondral Allograft and Meniscal Allograft Transplantation in the Knee

Background

Patient nonadherence with prescribed rehabilitation protocols is associated with up to 16 times higher likelihood of treatment failure after osteochondral allograft transplantation (OCA) and meniscal allograft transplantation.

Hypothesis

Patients who completed counseling with an orthopaedic health behavior psychologist as part of an evidence-based shift in practice at our institution would have significantly lower rates of nonadherence and surgical treatment failure versus patients who did not participate in counseling.

Study Design

Cohort study; Level of evidence, 2.

Methods

Patients in a prospective registry who underwent OCA and/or meniscal allograft transplantation between January 2016 and April 2021 were included for analysis when 1-year follow-up data were available. Of 292 potential patients, 213 were eligible for inclusion. Patients were categorized based on whether they participated in the preoperative counseling and postoperative patient management program: no health psych group (n = 172) versus health psych group (n = 41). Nonadherence was defined as documented evidence of a deviation from the prescribed postoperative rehabilitation protocol.

Results

In this cohort of patients, 50 (23.5%) were documented to be nonadherent. Patients in the no health psych cohort were significantly more likely to be nonadherent (P = .023; odds ratio [OR], 3.4). Tobacco use (OR, 7.9), higher preoperative Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Interference score, lower preoperative PROMIS Mental Health score, older age, and higher body mass index were also significantly associated with nonadherence (P < .001 for all). Patients who were nonadherent with the prescribed postoperative rehabilitation protocol during the first year after transplantation were 3 times more likely (P = .004) to experience surgical treatment failure than those who were adherent. Overall, 26.2% of patients in the no health psych group experienced surgical treatment failure versus 12.2% in the health psych cohort.

Conclusion

Data from the present study suggest that preoperative counseling with a health behavior psychologist is associated with an improved rate of patient adherence and a lower proportion of surgical treatment failure after OCA and meniscal allograft transplantation. Patients who remained adherent to the postoperative protocol were 3 times more likely to have a successful short-term (≥1 year) outcome.

Fabrication of 3D Bioprinted Bi-Phasic Scaffold for Bone–Cartilage Interface Regeneration

Treatments for osteochondral defects (OCDs) are mainly palliative and, with the increase in this pathology seen among both young and elderly people, an alternative treatment modality is sought. Many tissue-engineered strategies have been explored for regenerating the cartilage–bone interface; however, they generally fall short of being ideal. Although cell-laden hydrogel scaffolds are a common approach for bone and cartilage tissue regeneration, they usually lack homogenous cell dispersion and patient specificity. In this study, a biphasic 3D bioprinted composite scaffold was fabricated for cartilage–bone interface regeneration. To overcome the shortcoming of both materials, alginate–gelatin (A–G) hydrogel was used to confer a naturally occurring environment for the cells and polycaprolactone (PCL) was used to enhance mechanical stability, thus maximizing the overall performance. Hydroxyapatite fillers were added to the PCL in the bone phase of the scaffold to improve its bioactivity. Physical and biological evaluation of scaffolds in both phases was assessed. The scaffolds demonstrated a desirable biological response both singly and in the combined PCL/A-G scaffolds, in both the short term and longer term, showing promise as an interfacial material between cartilage and bone.

Rehabilitation Variability Following Osteochondral Autograft and Allograft Transplantation of the Knee

OBJECTIVE

The aim of this study is to assess the variability of postoperative rehabilitation protocols used by orthopedic surgery residency programs for osteochondral autograft transplantation (OAT) and osteochondral allograft transplantation (OCA) of the knee.

DESIGN

Online postoperative OAT and OCA rehabilitation protocols from US orthopedic programs and the scientific literature were reviewed. A custom scoring rubric was developed to analyze each protocol for the presence of discrete rehabilitation modalities and the timing of each intervention.

RESULTS

A total of 16 programs (10.3%) from 155 US academic orthopedic programs published online protocols and a total of 35 protocols were analyzed. Twenty-one protocols (88%) recommended immediate postoperative bracing following OAT and 17 protocols (100%) recommended immediate postoperative bracing following OCA. The average time protocols permitted weight-bearing as tolerated (WBAT) was 5.2 weeks (range = 0-8 weeks) following OAT and 6.2 weeks (range = 0-8 weeks) following OCA. There was considerable variation in the inclusion and timing of strength, proprioception, agility, and pivoting exercises. Following OAT, 2 protocols (8%) recommended functional testing as criteria for return to sport at an average time of 12.0 weeks (range = 12-24 weeks). Following OCA, 1 protocol (6%) recommended functional testing as criteria for return to sport at an average time of 12.0 weeks (range = 12-24 weeks).

CONCLUSION

A minority of US academic orthopedic programs publish OAT and OCA rehabilitation protocols online. Among the protocols currently available, there is significant variability in the inclusion of specific rehabilitation components and timing of many modalities. Evidence-based standardization of elements of postoperative rehabilitation may help improve patient care and subsequent outcomes.

Quality and Variability of Physical Therapy Protocols Varies Widely for Osteochondral Allograft Transplantation of the Femoral Condyles

OBJECTIVE

To assess the quality and variability of osteochondral allograft (OCA) transplantation rehabilitation protocols associated with academic orthopedic programs in the United States.

DESIGN

A systematic review was performed to collect all publicly available online rehabilitation protocols for femoral condyle OCA transplant from US academic orthopedic programs participating in the Electronic Residency Application Service. These protocols were evaluated for inclusion of different rehabilitation components as well as timing of suggested initiation of these activities.

RESULTS

A total of 22 protocols were included. Although 91% of protocols recommended bracing, wide variation exists in total time of utilization. Median time for full weight bearing (FWB) was 7 weeks (range 4-8). On average, each protocol mentioned 9 (range 2-18) different strengthening exercises. The median time suggested to return to high-impact activities was 9 months (range 8-12). Only 3 protocols (14%) offered criteria of advancement for each phase as well as criteria for discharge.

CONCLUSION

Very few of the academic orthopedic programs have published online rehabilitation protocols following OCA transplantation. Although there is wide variation between the protocols, it allowed the identification of trends or patterns that are more common. However, there is need for more standardized evidence-based rehabilitation protocols which are easy to understand and follow by patients.

Local curvature mismatch may worsen the midterm functional outcomes of osteochondral allograft transplantation

PURPOSE

This study aimed to determine the magnitude of local curvature matching in the sagittal plane between an implanted graft and the condylar region receiving the graft and to analyze its effect on clinical outcomes in patients undergoing osteochondral allograft transplantation (OCA).

METHODS

Patients who underwent knee OCA between 2016 and 2019 without circumferential step-off and were matched with a donor in accordance with the conventional matching process were included. The magnitude of donor-host local curvature matching was measured using postoperative sagittal magnetic resonance imaging data with Syngo (Siemens Medical Solutions, Forchheim, Germany) and GeoGebra (GeoGebra GmbH, Linz, AU) software. In addition to radiological evaluation, ROC analysis was performed to compare the patient-reported outcome measures (PROMs) obtained during the 2-year follow-up period among the patients in the SagA group, who had a graft match in the sagittal plane; SagB group, who had low convexity of the graft in the sagittal plane; and SagC group, who had high convexity of the graft in the sagittal plane in accordance with the determined indices.

RESULTS

The study included 27 patients who fulfilled the inclusion criteria, and the mean clinical scores of the SagC group were not statistically significantly higher than those of the other groups at any timepoint during the follow-up. The mean Tegner, IKDC, total KOOS and SF-12 physical and mental health scores of the SagC group were lower than those of the other two groups at various follow-up time points, particularly at month 24 (p < 0.05). There were no significant differences between the SagA and SagB groups in the PROMs at any of the follow-up time points (n.s.). The significant differences observed between the SagC group and the other groups in the mean KOOS scores for function in daily living and function in sport and recreation were also observed between the SagA and SagB groups at the follow-ups (p < 0.05).

CONCLUSION

During OCA, a local curvature mismatch between the donor and the host involving large graft convexity may have a negative impact on midterm clinical outcomes. A preoperative analysis of the convexity relationship between the defect site and the graft region in the hemicondylar allograft to be used may enhance donor-host matching. The local analysis method described in the current study may also facilitate graft supply by ensuring donor-host matching without condyle-side and size matching.

LEVEL OF EVIDENCE

III.

Thoughts on cartilage tissue engineering: A 21st century perspective

In mature individuals, hyaline cartilage demonstrates a poor intrinsic capacity for repair, thus even minor defects could result in progressive degeneration, impeding quality of life. Although numerous attempts have been made over the past years for the advancement of effective treatments, significant challenges still remain regarding the translation of in vitro cartilage engineering strategies from bench to bedside. This paper reviews the latest concepts on engineering cartilage tissue in view of biomaterial scaffolds, tissue biofabrication, mechanobiology, as well as preclinical studies in different animal models. The current work is not meant to provide a methodical review, rather a perspective of where the field is currently focusing and what are the requirements for bridging the gap between laboratory-based research and clinical applications, in light of the current state-of-the-art literature. While remarkable progress has been accomplished over the last 20 years, the current sophisticated strategies have reached their limit to further enhance healthcare outcomes. Considering a clinical aspect together with expertise in mechanobiology, biomaterial science and biofabrication methods, will aid to deal with the current challenges and will present a milestone for the furtherance of functional cartilage engineering.

Osteochondral Allograft Transplantation in Professional Athletes: Rehabilitation and Return to Play

For the treatment of large chondral and osteochondral defects of the knee, osteochondral allograft transplantation (OCA) is an effective solution with relatively high rates of return to sport. In professional athletes, rehabilitation following OCA is a critical component of the process of returning the athlete to full sports activity and requires a multidisciplinary team approach with frequent communication between the surgical and rehabilitation teams (physical therapists, athletic trainers, coaching staff). In this review, we describe our five-phase approach to progressive rehabilitation of the professional athlete after OCA, which takes into account the biological processes of healing and optimization of neuromuscular function required for the demands of elite-level sport. The principles of early range of motion, proper progression through the kinetic chain, avoidance of pain and effusion, optimization of movement, regimen individuation, and integration of sports-specific activities underlie proper recovery.

Influence of the Mechanical Environment on the Regeneration of Osteochondral Defects

Articular cartilage is a highly specialised connective tissue of diarthrodial joints which provides a smooth, lubricated surface for joint articulation and plays a crucial role in the transmission of loads. In vivo cartilage is subjected to mechanical stimuli that are essential for cartilage development and the maintenance of a chondrocytic phenotype. Cartilage damage caused by traumatic injuries, ageing, or degradative diseases leads to impaired loading resistance and progressive degeneration of both the articular cartilage and the underlying subchondral bone. Since the tissue has limited self-repairing capacity due its avascular nature, restoration of its mechanical properties is still a major challenge. Tissue engineering techniques have the potential to heal osteochondral defects using a combination of stem cells, growth factors, and biomaterials that could produce a biomechanically functional tissue, representative of native hyaline cartilage. However, current clinical approaches fail to repair full-thickness defects that include the underlying subchondral bone. Moreover, when tested in vivo, current tissue-engineered grafts show limited capacity to regenerate the damaged tissue due to poor integration with host cartilage and the failure to retain structural integrity after insertion, resulting in reduced mechanical function. The aim of this review is to examine the optimal characteristics of osteochondral scaffolds. Additionally, an overview on the latest biomaterials potentially able to replicate the natural mechanical environment of articular cartilage and their role in maintaining mechanical cues to drive chondrogenesis will be detailed, as well as the overall mechanical performance of grafts engineered using different technologies.