Is American Joint Replacement Registry Data Consistent With International Survivorship in Hip and Knee Arthroplasty? A Comparative Analysis.

BACKGROUND: In collaboration with the Orthopedic Data Evaluation Panel (ODEP), the American Joint Replacement Registry (AJRR) investigated the consistency of hip and knee arthroplasty survivorship results compared to the UK National Joint Registry (NJR). METHODS: A total of three primary knee devices and three primary hip devices were selected by AJRR and ODEP with known variation in performance. Implant manufacturers independently produced Kaplan Meier survivorship based on NJR data and submitted to ODEP for comparison. The AJRR mirrored the methodology, and results from both sources were stratified into three cohorts (all-age, < 65, and ≥ 65 years). RESULTS: There were 42,671 AJRR and 60,439 NJR primary knee cases and 70,169 AJRR and 422,657 NJR primary total hip arthroplasty cases. For TKA, performance between the AJRR and NJR were consistent, showing similar trends for comparatively high and low performing devices. Both PS and CR devices showed statistical agreement in survivorship for all 3 cohorts. Unicompartmental comparison also showed statistical agreement for the Medicare cohort. The all-age and < 65-year-old cohorts showed similar trends and reached statistical agreement through 7 and 6 years. For total hip arthroplasty, performance between the AJRR and NJR were consistent, showing similar trends for comparatively high and low performing devices; 0.18% average difference in survivorship at final follow-up (8 years). One femoral device did not reach statistical agreement but showed only 0.61% difference in survivorship. The remaining acetabular and femoral devices reached statistical agreement in all-ages and through 7 and 8 years in the ≥ 65-year-old cohort. CONCLUSIONS: AJRR and NJR performance trends and survivorship were similar across hip and knee arthroplasty with greatest consistency in the all-age and ≥ 65 cohorts. This focused comparison of survivorship showed encouraging results for reliability of patient outcomes in AJRR compared to the world's largest joint arthroplasty registry which has strong implications for global improvement in patient safety.

Machine learning models to predict surgical case duration compared to current industry standards: scoping review.

BACKGROUND: Surgical waiting lists have risen dramatically across the UK as a result of the COVID-19 pandemic. The effective use of operating theatres by optimal scheduling could help mitigate this, but this requires accurate case duration predictions. Current standards for predicting the duration of surgery are inaccurate. Artificial intelligence (AI) offers the potential for greater accuracy in predicting surgical case duration. This study aimed to investigate whether there is evidence to support that AI is more accurate than current industry standards at predicting surgical case duration, with a secondary aim of analysing whether the implementation of the models used produced efficiency savings. METHOD: PubMed, Embase, and MEDLINE libraries were searched through to July 2023 to identify appropriate articles. PRISMA extension for scoping reviews and the Arksey and O'Malley framework were followed. Study quality was assessed using a modified version of the reporting guidelines for surgical AI papers by Farrow et al. Algorithm performance was reported using evaluation metrics. RESULTS: The search identified 2593 articles: 14 were suitable for inclusion and 13 reported on the accuracy of AI algorithms against industry standards, with seven demonstrating a statistically significant improvement in prediction accuracy (P < 0.05). The larger studies demonstrated the superiority of neural networks over other machine learning techniques. Efficiency savings were identified in a RCT. Significant methodological limitations were identified across most studies. CONCLUSION: The studies suggest that machine learning and deep learning models are more accurate at predicting the duration of surgery; however, further research is required to determine the best way to implement this technology.

Clinical investigations to evaluate high-risk orthopaedic devices: a systematic review of the peer-reviewed medical literature.

Purpose: The objective of this systematic review was to give an overview of clinical investigations regarding hip and knee arthroplasty implants published in peer-reviewed scientific medical journals before entry into force of the EU Medical Device Regulation in May 2021. Methods: We systematically reviewed the medical literature for a random selection of hip and knee implants to identify all peer-reviewed clinical investigations published within 10 years before and up to 20 years after regulatory approval. We report study characteristics, methodologies, outcomes, measures to prevent bias, and timing of clinical investigations of 30 current implants. The review process was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: We identified 2912 publications and finally included 151 papers published between 1995 and 2021 (63 on hip stems, 34 on hip cups, and 54 on knee systems). We identified no clinical studies published before Conformité Européene (CE)-marking for any selected device, and no studies even up to 20 years after CE-marking in one-quarter of devices. There were very few randomized controlled trials, and registry-based studies generally had larger sample sizes and better methodology. Conclusion: The peer-reviewed literature alone is insufficient as a source of clinical investigations of these high-risk devices intended for life-long use. A more systematic, efficient, and faster way to evaluate safety and performance is necessary. Using a phased introduction approach, nesting comparative studies of observational and experimental design in existing registries, increasing the use of benefit measures, and accelerating surrogate outcomes research will help to minimize risks and maximize benefits.

Processes for Designing Innovative Biomedical Hardware to Use in Space and on Earth.

The new era of space exploration is increasing the astronaut's number and diversity in low orbit and beyond. The influx of such a diverse crew population will also increase the need for medical technologies to ensure safe and productive missions. Such a need represents a unique opportunity to innovate and develop diagnostics and treatment tools to meet future needs. Historically, terrestrial regulatory oversight of biomedical design processes was considered separate from spaceflight regulatory processes because it did not address spaceflight constraints. These constraints challenge the creative development of unique solutions for use in space. Translation between healthcare innovation in spaceflight to healthcare on Earth and vice versa requires understanding the commonalities, unique needs and constraints. This manuscript provides a framework for comparing Earth-space design processes and a perspective on the best practices to improve healthcare equity and health outcomes.

Artificial intelligence for image analysis in total hip and total knee arthroplasty : a scoping review.

AIMS: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are common orthopaedic procedures requiring postoperative radiographs to confirm implant positioning and identify complications. Artificial intelligence (AI)-based image analysis has the potential to automate this postoperative surveillance. The aim of this study was to prepare a scoping review to investigate how AI is being used in the analysis of radiographs following THA and TKA, and how accurate these tools are. METHODS: The Embase, MEDLINE, and PubMed libraries were systematically searched to identify relevant articles. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews and Arksey and O'Malley framework were followed. Study quality was assessed using a modified Methodological Index for Non-Randomized Studies tool. AI performance was reported using either the area under the curve (AUC) or accuracy. RESULTS: Of the 455 studies identified, only 12 were suitable for inclusion. Nine reported implant identification and three described predicting risk of implant failure. Of the 12, three studies compared AI performance with orthopaedic surgeons. AI-based implant identification achieved AUC 0.992 to 1, and most algorithms reported an accuracy > 90%, using 550 to 320,000 training radiographs. AI prediction of dislocation risk post-THA, determined after five-year follow-up, was satisfactory (AUC 76.67; 8,500 training radiographs). Diagnosis of hip implant loosening was good (accuracy 88.3%; 420 training radiographs) and measurement of postoperative acetabular angles was comparable to humans (mean absolute difference 1.35° to 1.39°). However, 11 of the 12 studies had several methodological limitations introducing a high risk of bias. None of the studies were externally validated. CONCLUSION: These studies show that AI is promising. While it already has the ability to analyze images with significant precision, there is currently insufficient high-level evidence to support its widespread clinical use. Further research to design robust studies that follow standard reporting guidelines should be encouraged to develop AI models that could be easily translated into real-world conditions. Cite this article: Bone Joint J 2022;104-B(8):929-937.

EFORT recommendations for off-label use, mix & match and mismatch in hip and knee arthroplasty.

Off-label use is frequently practiced in primary and revision arthroplasty, as there may be indications for the application of implants for purposes outside the one the manufacturers intended.Under certain circumstances, patients may benefit from selective application of mix & match. This can refer to primary hip arthroplasty (if evidence suggests that the combination of devices from different manufacturers has superior results) and revision hip or knee arthroplasty (when the exchange of one component only is necessary and the invasiveness of surgery can be reduced).Within the EFORT 'Implant and Patient Safety Initiative', evidence- and consensus-based recommendations have been developed for the safe application of off-label use and mix & match in primary as well as revision hip and knee arthroplasty.Prior to the application of a medical device for hip or knee arthroplasty off-label and within a mix & match situation, surgeons should balance the risks and benefits to the patient, obtain informed consent, and document the decision process appropriately.Nevertheless, it is crucial for surgeons to only combine implants that are compatible. Mismatch of components, where their sizes or connections do not fit, may have catastrophic effects and is a surgical mistake.Surgeons must be fully aware of the features of the components that they use in off-label indications or during mix & match applications, must be appropriately trained and must audit their results.Considering the frequent practice of off-label and mix & match as well as the potential medico-legal issues, further research is necessary to obtain more data about the appropriate indications and outcomes for those procedures. Cite this article: EFORT Open Rev 2021;6:982-1005. DOI: 10.1302/2058-5241.6.210080.

Implant brand portfolios, the potential for camouflage of data, and the role of the Orthopaedic Data Evaluation Panel in total knee arthroplasty.

AIMS: Knee arthroplasty surgery is a highly effective treatment for arthritis and disorders of the knee. There are a wide variety of implant brands and types of knee arthroplasty available to surgeons. As a result of a number of highly publicized failures, arthroplasty surgery is highly regulated in the UK and many other countries through national registries, introduced to monitor implant performance, surgeons, and hospitals. With time, the options available within many brand portfolios have grown, with alternative tibial or femoral components, tibial insert materials, or shapes and patella resurfacings. In this study we have investigated the effect of the expansion of implant brand portfolios and where there may be a lack of transparency around a brand name. We also aimed to establish the potential numbers of compatible implant construct combinations. METHODS: Hypothetical implant brand portfolios were proposed, and the number of compatible implant construct combinations was calculated. RESULTS: A simple knee portfolio with cemented cruciate-retaining (CR) and posterior-stabilized (PS) components, with and without a patella, has four combinations. If there are two options available for each component, the numbers double for each option, resulting in 32 combinations. The effect of adding a third option multiplies the number by 1.3. Introducing compatible uncemented options, with the effect of hybrids, multiplies the number by 4. An implant portfolio with two femoral components (both in CR and PS), with two insert options and a patella, all in cemented and uncemented versions leads to 192 possible compatible implant construct combinations. There are implant brands available to surgeons with many more than two options. CONCLUSION: This study demonstrates that the addition of multiple variants within a knee brand portfolio leads to a large number (many hundreds) of compatible implant construct combinations. Revision rates of implant combinations are not currently reviewed at this level of granularity, leading to the risk of camouflage of true outcomes. Cite this article: Bone Joint J 2021;103-B(10):1555-1560.

MoM total hip replacements in Europe: a NORE report.

The purpose of this paper is to determine the prevalence of metal-on-metal (MoM) total hip replacement (THR) in European registries, to assess the incidence of revision surgery and to describe the national follow-up guidelines for patients with MoM THR including resurfacings.Eleven registries of the Network of Orthopaedic Registries of Europe (NORE) participated totalling 54 434 resurfacings and 58 498 large stemmed MoM THRs.The resurfacings and stemmed large head MoM had higher pooled revision rates at five years than the standard total hip arthroplasties (THA): 6.0%, 95% confidence interval (CI) 5.3 to 6.8 for resurfacings; 6.9%, 95% CI 4.4 to 9.4 for stemmed large head MoM; and 3.0%, 95% CI 2.5 to 3.6 for conventional THA.The resurfacings and stemmed large head MoM had higher pooled revision rates at ten years than the standard THAs: 12.1%, 95% CI 11.0 to 13.3 for resurfacings; 15.5%, 95% CI 9.0 to 22 for stemmed large head MoM; and 5.1%, 95% CI 3.8 to 6.4 for conventional THA.Although every national registry reports slightly different protocols for follow-up, these mostly consist of annual assessments of cobalt and chromium levels in blood and MRI (MARS) imaging. Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180078.

A Novel Minimally Invasive Technique for Treatment of Unicameral Bone Cysts.

Management of unicameral bone cysts (UBC) remain controversial. These cysts seldom heal spontaneously or even after pathological fracture. Sometimes these cysts can be very large and incredibly troublesome to the patient. Various treatments exist with variable success rates. We present our experience of treating these lesions by continuous drainage. Over a seven year period, six patients with unicameral bone cysts were treated by inserting a modified drain into the wall of the cyst. The aim of surgery was to place the drain in a dependent area of the cyst, through the cortex allowing for continuous drainage. This was achieved through a small incision under radiographic control. A cement restrictor (usually used for femoral canal plugging during total hip replacements) was modified and inserted to prevent closure of the drain site. A redivac drain was passed through the plug into the cyst. The drain was left in place for a week to establish an epithelialized pathway which hopefully would remain patent, into the subcutaneous tissues, after the drain had been removed. There were four males and two females in the group and the age range was 6 -12 years. Four of the lesions were in the upper humerus, one in the proximal femur and the other one in the proximal tibia. Healing was rated according to the modified Neer classification. Grade 1 (healed) and Grade 2 (healed with defect) was defined as excellent outcome. Persistent /Recurrent cysts (Grade 3 and 4) were noted as unsatisfactory. Five cases were completely healed. Only one had a further fracture and there were no recurrent fractures. All the patients reported complete comfort and they all were able to re-engage in recreational activities without restriction. We think that reducing the intra-medullary pressure in these lesions will lead to healing. We report a safe and minimally invasive technique for the management of UBC.

Mixing of components from different manufacturers in total hip arthroplasty: prevalence and comparative outcomes.

BACKGROUND AND PURPOSE: There have recently been highly publicized examples of suboptimal outcomes with some newer implant designs used for total hip replacement. This has led to calls for tighter regulation. However, surgeons do not always adhere to the regulations already in place and often use implants from different manufacturers together to replace a hip, which is against the recommendations of the Medicines and Healthcare Products Regulatory Agency (MHRA) and the directions of the manufacturers. PATIENTS AND METHODS: We used data from the National Joint Registry of England and Wales (NJR) to investigate this practice. RESULTS: Mixing of components was common, and we identified over 90,000 cases recorded between 2003 and 2013. In the majority of these cases (48,156), stems and heads from one manufacturer were mixed with polyethylene cemented cups from another manufacturer. When using a cemented stem and a polyethylene cup, mixing of stems from one manufacturer with cups from another was associated with a lower revision rate. At 8 years, the cumulative percentage of revisions was 1.9% (95% CI: 1.7-2.1) in the mixed group as compared to 2.4% (2.3-2.5) in the matched group (p = 0.001). Mixing of heads from one manufacturer with stems from another was associated with a higher revision rate (p < 0.001). In hip replacements with ceramic-on-ceramic or metal-on-metal bearings, mixing of stems, heads, and cups from different manufacturers was associated with similar revision rates (p > 0.05). INTERPRETATION: Mixing of components from different manufacturers is a common practice, despite the fact that it goes against regulatory guidance. However, it is not associated with increased revision rates unless heads and stems from different manufacturers are used together.

Cobalt from metal-on-metal hip replacements may be the clinically relevant active agent responsible for periprosthetic tissue reactions.

Some types of metal-on-metal (MOM) hip replacements have unacceptably high rates of failure, such as the Ultima TPS MOM hip, with 13.8% failure at 5 years. This has been attributed to an inflammatory reaction following the release of cobalt (Co) and chromium (Cr) from the bearing surfaces and modular junctions. There is in vitro evidence that Co is more important than Cr in the inflammatory process, but there are no reported human tissue studies of the analysis of implant-derived metals.

Monitoring the introduction and performance of a joint replacement: the United Kingdom metal-on-metal alert.

Recent events have made us question our ability to monitor the introduction and performance of a new prosthetic joint replacement. These concerns are mirrored in many other countries, even those with joint registries and other systems for detecting poorly performing implants. In the United Kingdom, as is the case in most European Union countries, we have assessment processes in place, particularly the CE (Conformité Européenne) mark, the National Joint Registry, and the Orthopaedic Data Evaluation Panel. It is important to realize that these organizations can only react to poor performance; it is not within their power as monitoring agencies to prevent a poor implant from entering the market. When an implant has been shown to perform badly, it is referred to the Medicines and Healthcare products Regulatory Agency (MHRA), which then discusses the report with the manufacturer. When it is deemed that there is unequivocal evidence of a serious problem with the implant, the MHRA issues alerts to all hospitals and practitioners. We have continuing concerns about how to assess and monitor modifications to already existing devices. Suggestions are made for improvements to this system, and the authors will welcome feedback.

A multinational assessment of metal-on-metal bearings in hip replacement.

There is emerging evidence that many metal-on-metal (MoM) bearings, when used with large femoral heads in conventional hip replacement and some resurfacing prostheses, are associated with increased rates of revision arthroplasty. Registries are the main sources of data on MoM prostheses. At the recent International Consortium of Orthopaedic Registries (ICOR) meeting, data were presented from the Australian, England and Wales, and New Zealand registries. All registries reported an increased rate of revision for large femoral head MoM prostheses when prostheses were aggregated compared with the aggregated data of hip prostheses with other bearing surfaces. There was also evidence, however, that the outcome varied, depending on the type of prostheses used, in both large femoral head MoM conventional hip replacement as well as resurfacing hip replacement.The relevance of the recent isolated case reports on systemic metal toxicity was also discussed at the ICOR meeting. Although systemic metal toxicity appears to be a rare occurrence, there is a need to undertake appropriately designed studies to define the true prevalence of this phenomenon. There may be advantages in nesting these studies within registries. The ICOR meeting highlighted the implications of the MoM experience for the orthopaedic industry, regulators, and surgeons.

Can choices between alternative hip prostheses be evidence based? a review of the economic evaluation literature.

BACKGROUND: Total hip replacement surgery places a considerable financial burden on health services and society. Given the large number of hip prostheses available to surgeons, reliable economic evidence is crucial to inform resource allocation decisions. This review summarises published economic evidence on alternative hip prostheses to examine the potential for the literature to inform resource allocation decisions in the UK. METHODS: We searched nine medical and economics electronic databases. 3,270 studies were initially identified, 17 studies were included in the review. Studies were critically appraised using three separate guidelines. RESULTS: Several methodological problems were identified including a lack of observed long term prosthesis survival data, limited up-to-date and UK based evidence and exclusion of patient and societal perspectives. CONCLUSIONS: More clinical trials including long term follow-up and economic evaluation are needed. These should compare the cost-effectiveness of different prostheses with longer-term follow-up and including a wider perspective.

Community-based orthopaedic follow-up. Is it what doctors and patients want?

INTRODUCTION: The objective of this study was to investigate how patients, general practitioners (GPs) and orthopaedic trainees, feel about the proposed governmental changes to reduce orthopaedic out-patient clinics by having GPs and specialist nurses follow-up postoperative orthopaedic patients in the community. SUBJECTS AND METHODS: The design was a cross-sectional questionnaire study including a teaching hospital and general practitioners in the Norfolk primary care trust. Participants were 73 orthopaedic postoperative patients who attended out-patients over a 1-week period in July 2007 who all responded. Of 250 GPs, 239 responded. Of 38 orthopaedic trainees at the level of senior house officer (post MRCS) and specialist registrar (Eastern Deanery Rotation and Pott Rotation), 30 responded RESULTS: Of the 73 patients, 56 (77%) felt the surgeon was best suited to manage them postoperatively. Of these, 47 felt that it was very important that the surgical team saw them postoperatively. Also, 53 felt that their GP did not have sufficient knowledge and experience to deal with their current orthopaedic problem adequately. Only 12 GPs of 239 (5%) felt very confident assessing postoperative patients. Inadequate resources available to diagnose and treat postoperative complications was noted by 74% as the reason for not performing follow-up in primary care, and only 18% felt they should follow-up postoperative patients. All trainees felt that following up their own postoperative patients was important to their training. CONCLUSIONS: Most patients, GPs, and orthopaedic trainees had serious doubts about the proposed governmental changes to reduce orthopaedic out-patient clinics by having GPs and specialist nurses follow-up postoperative orthopaedic patients in the community.

Revision rates after primary hip and knee replacement in England between 2003 and 2006.

BACKGROUND: Hip and knee replacement are some of the most frequently performed surgical procedures in the world. Resurfacing of the hip and unicondylar knee replacement are increasingly being used. There is relatively little evidence on their performance. To study performance of joint replacement in England, we investigated revision rates in the first 3 y after hip or knee replacement according to prosthesis type. METHODS AND FINDINGS: We linked records of the National Joint Registry for England and Wales and the Hospital Episode Statistics for patients with a primary hip or knee replacement in the National Health Service in England between April 2003 and September 2006. Hospital Episode Statistics records of succeeding admissions were used to identify revisions for any reason. 76,576 patients with a primary hip replacement and 80,697 with a primary knee replacement were included (51% of all primary hip and knee replacements done in the English National Health Service). In hip patients, 3-y revision rates were 0.9% (95% confidence interval [CI] 0.8%-1.1%) with cemented, 2.0% (1.7%-2.3%) with cementless, 1.5% (1.1%-2.0% CI) with "hybrid" prostheses, and 2.6% (2.1%-3.1%) with hip resurfacing (p < 0.0001). Revision rates after hip resurfacing were increased especially in women. In knee patients, 3-y revision rates were 1.4% (1.2%-1.5% CI) with cemented, 1.5% (1.1%-2.1% CI) with cementless, and 2.8% (1.8%-4.5% CI) with unicondylar prostheses (p < 0.0001). Revision rates after knee replacement strongly decreased with age. INTERPRETATION: Overall, about one in 75 patients needed a revision of their prosthesis within 3 y. On the basis of our data, consideration should be given to using hip resurfacing only in male patients and unicondylar knee replacement only in elderly patients.

Open reduction of developmental hip dysplasia using a medial approach: a review of 24 hips.

The results of the Ferguson medial approach for reduction of developmental hip dysplasia were reviewed for 24 hips. The mean age at surgery was 4.8 months and the mean length of clinical follow-up was 59 months. Clinically all hips were normal in follow-up and radiologically the acetabular index was within normal limits. There was the need for further surgery in two cases with loss of concentric reduction. There were two cases showing evidence of vascular insult post operatively according to the classification of Kalmachi and MacEwan. We conclude that the Ferguson medial approach is a safe and effective form of treatment for open reduction of developmental hip dysplasia in cases where closed reduction either has failed or is inappropriate. The age of the child or the presence of the upper femoral ossific nucleus does not appear to affect outcome. The procedure can safely be performed before six months of age.

The long-term outcome of tendon lengthening for chronic Achilles tendon pain.

BACKGROUND: The purpose of this study was to assess the long-term results of tendon lengthening surgery for the treatment of chronic Achilles tendon pain. METHODS: The results of 21 procedures in 18 patients were assessed. Each patient had an open Z-plasty to lengthen the Achilles tendon by 1 cm. RESULTS: Results showed a long-term (7.5 years) reduction in visual analogue pain scores for sporting activity in 20 of 21 procedures (median 50 point reduction, p < 0.0005). The tendon lengthening was apparent in a mean increase in dorsiflexion of 5 degrees. Two patients had minor gait abnormalities postoperatively. One patient had a reduction in plantarflexion power on the operated side, but five patients had improved power compared to the nonoperated limb. One major and five minor surgical complications were noted. CONCLUSIONS: The retrospective nature of this study must be noted in drawing conclusions. However, the results suggest excellent long-term reduction of Achilles pain after tendon lengthening. This must be weighed against a relatively high complication rate for any procedure in this region. This treatment does not appear to cause long-term deficits in plantarflexion power or gait.

The effect of achilles tendon lengthening on ankle dorsiflexion: a cadaver study.

BACKGROUND: Tendon lengthening is an important cause of morbidity after Achilles tendon rupture. However, direct measurement of the tendon length is difficult. Ankle dorsiflexion has, therefore, been used as a surrogate measure on the assumption that it is the Achilles tendon that limits this movement. The aim of this investigation was to assess the relationship between Achilles tendon length and ankle dorsiflexion. The primary question was whether or not the Achilles tendon is the structure that limits ankle dorsiflexion. The secondary purpose was to quantify the relationship between Achilles tendon lengthening and dorsiflexion at the ankle joint. METHODS: Five cadaver specimens were dissected to expose the tendons and capsular tissue of the leg and hindfoot. Fixed bony reference points were used as markers for the measurements. In the first specimen, the Achilles tendon was intact and the other structures that may limit ankle dorsiflexion were sequentially divided. In the other specimens the Achilles tendon was lengthened by 1 cm intervals and the effect upon ankle dorsiflexion movement was recorded. RESULTS: Division of the other tendons and the capsular tissue around the ankle joint did not affect the range of ankle dorsiflexion. When the Achilles was divided the foot could be dorsiflexed until the talar neck impinged upon the anterior aspect of the distal tibia. There was a mean increase of 12 degrees of dorsiflexion for each centimeter increase in tendon length. CONCLUSION: The Achilles tendon is the anatomical structure that limits ankle dorsiflexion, even when the tendon is lengthened. There was a linear relationship between the length of the Achilles tendon and the range of ankle dorsiflexion in this cadaver model. Ankle dorsiflexion would appear to be a clinically useful indicator of tendon length.