Clinical and Functional Outcomes After ACL Reconstruction Versus Primary Repair

The anterior cruciate ligament (ACL), one of the key stabilizers of the knee joint, plays a crucial role in maintaining both anteroposterior and rotational stability. The increasing popularity of recreational and competitive sports has contributed to a rising incidence of ACL injuries in recent years. Until the late 1980s, primary repair was widely accepted as the standard treatment for ACL injuries. Although short-term outcomes were generally satisfactory, this technique was largely abandoned due to high failure rates observed in medium- and long-term follow-ups. The probable causes of these unfavorable outcomes include suboptimal patient selection, invasive open repair techniques performed with absorbable sutures, and nonfunctional rehabilitation approaches characterized by prolonged cast immobilization. Considering the limited healing potential of the ligament, reconstruction surgery-performed using allografts or autologous tendon grafts-emerged as the new standard for the treatment of ACL injuries.

However, several disadvantages associated with reconstruction have raised the notion that a single surgical method may not be appropriate for all patients. These drawbacks include graft rerupture or contralateral ACL injury, loss of proprioception, physeal disturbances in pediatric populations, donor site morbidity in autografts or higher failure rates in allografts, the potential need for complex revision surgery, and the risk of early-onset osteoarthritis. In recent years, advances in patient selection criteria, minimally invasive surgical techniques, and modern rehabilitation protocols have renewed interest in arthroscopic primary ACL repair. This method preserves the native ligament and its proprioceptive properties while avoiding donor site morbidity, thereby offering the potential for a smoother and more accelerated postoperative rehabilitation process. Additionally, if primary repair fails, ACL reconstruction remains a viable subsequent treatment option. Primary repair has been described as a less morbid surgical alternative for patients presenting with acute proximal ACL tears, although high-quality evidence for its use is still limited.

Recent studies have shown improved success rates following primary repair of proximal ACL tears. In one investigation, researchers reported a 0% failure rate among 75 patients treated with primary ACL repair. Furthermore, 88% of patients demonstrated a negative pivot-shift test, 87% exhibited 0 or +1 Lachman test findings, and 89% successfully returned to sport. Similarly, numerous studies have evaluated the clinical effectiveness of ACL repair, and several recent systematic reviews have suggested that primary repair may be an effective treatment strategy with reasonable clinical outcomes compared to ACL reconstruction. Nonetheless, concerns remain that some evidence includes older cohorts that may not reflect contemporary surgical practices. A systematic review of only five comparative studies found no significant differences between treatments regarding clinical outcome scores, knee laxity, or graft rerupture rates. More recent randomized controlled trials have yielded conflicting results; some authors report that ACL repair provides non-inferior clinical outcomes compared to reconstruction, while others emphasize higher rates of adverse events and failure associated with repair. These issues underscore the need for further research comparing the medium- to long-term outcomes of ACL repair and ACL reconstruction.

Given the recent increase in clinical studies evaluating ACL repair versus reconstruction, synthesizing and expanding evidence from such research is critical for achieving a comprehensive and transparent understanding of the advantages, disadvantages, and clinical implications of both procedures.

The purpose of the present study is to compare postoperative clinical outcomes and patient-reported measures in individuals undergoing ACL reconstruction or primary ACL repair. Long-term outcomes of both procedures will be examined in terms of knee flexor and extensor muscle strength and endurance, torque-generating capacity and fatigue resistance, muscle oxygenation, knee joint proprioception, lower-extremity balance, and knee laxity. In this context, the findings of this study aim to provide valuable insights that may inform postoperative rehabilitation strategies and contribute to evidence-based clinical decision-making.

Inclusion criteria

for the ACL Reconstruction Group

• Age 18-40 years
• History of complete ACL rupture treated with ACL reconstruction
• Surgery performed at Gazi University Department of Orthopedics and Traumatology
• At least 12 months postoperative at the time of evaluation
• Ability to comply with all study procedures
• Signed informed consent

Exclusion criteria

for the ACL Reconstruction Group

• Previous surgery for partial or chronic ACL tear
• Concomitant multi-ligament knee injuries
• Prior surgery on the ipsilateral or contralateral knee
• Lower extremity malalignment (e.g., significant varus/valgus)
• Tibial avulsion-type ACL injury
• Neurological or musculoskeletal disorders affecting lower limb function
• Any medical condition that may interfere with test performance or safety

Inclusion criteria

for the Primary ACL Repair Group

• Age 18-40 years
• Complete ACL rupture treated with arthroscopic primary ACL repair
• Surgery performed at Gazi University Department of Orthopedics and Traumatology
• Minimum 12 months postoperative at the time of assessment A-bility to follow and complete study procedures
• Signed informed consent

Exclusion criteria

for the Primary ACL Repair Group

• Previous surgery for partial or chronic ACL injury
• Multi-ligament knee injuries
• History of surgery on either knee
• Lower extremity malalignment
• Tibial avulsion-type ACL rupture
• Neuromuscular or musculoskeletal diseases affecting lower limb function or balance
• Any condition that may affect participation or compromise safety

Inclusion criteria

for the Healthy Control Group

• Age 18-40 years
• No significant lower-extremity malalignment (e.g., varus/valgus deformity)
• No history of lower-extremity injury within the past 12 months
• No known chronic systemic disease
• No history of knee surgery or diagnosed knee pathology
• Ability to understand and comply with study procedures
• Signed informed consent

Exclusion criteria

for the Healthy Control Group

• Presence of clinically significant lower-extremity malalignment
• Lower-extremity musculoskeletal injury within the last 12 months
• Any chronic systemic or metabolic disease
• History of knee injury, knee surgery, or diagnosed knee pathology
• Neurological, vestibular, or musculoskeletal disorder affecting balance or gait
• Inability to complete study procedures