Outcome analysis of posterior cruciate ligament injuries

Background and rationale

In the knee joint complex, cruciate ligaments are of great importance as they provide maximal restrain to the translation of tibia over the femur.¹ The posterior cruciate ligament with its attachment at the antero-lateral aspect of medial condyle of femur proximally and distally at the tibial plateau, gives primary restrain to posterior translation of tibia over femur.² It, to some extent, also works to resist the valgus and varus forces.³ Injury to this ligament occurs less often than to the other cruciate ligament of the knee complex. It has a cross sectional area of 11-13 mm², making it twice as thick as the anterior cruciate ligament and a tensile strength of 739 to 1627 Newton.⁴

A posteriorly directed strong force is required to damage both the postero-medial and antero-lateral bundles of the posterior cruciate ligament (PCL) and this usually occurs with knee in flexion.⁵ Dashboard injuries following motor vehicle accidents are the most common causative factors.⁶ Additionally, falling forward onto a flexed knee might result in PCL damage. In baseball, football, skiing and rugby, PCL injuries are the most frequent sports-related injuries. Less frequently, harm to the knee joint might result from a rotational hyperextension injury.^7,8

Injury to this ligament accounts for only 20% of the ligament injuries of the knee. PCL sprains or tears usually occur with the involvement of other ligaments, making isolated PCL injuries a rare occurrence.⁹ A study conducted in 2003 stated that motor vehicle accidents and sport injuries account for 45% and 40% of PCL injuries respectively, with the average age of receiving these injuries being 27 years old. Falls on a flexed knee with foot plantar flexed accounted for 24%.^10,11

The ligament is further divided into two parts: the antero-lateral bundle, making up 65% of the ligament, and the postero-medial bundle, making up 35%.¹² The postero-medial bundle is taut with knee in extension and the anterolateral bundle is taut in knee flexion.¹³ It provides greatest restrain between 30-90 degrees of knee flexion.¹⁴ Since injuries to the flexion are more common, the anterolateral bundle is more susceptible to sprains and tears,¹⁵ although literature on pure isolated injuries of the two bundles is scarce.¹⁶ The middle geniculate artery supplies blood to the PCL, which also is innervated by the tibial nerve.¹⁷ At 90 degrees, 95% of the posterior translational forces are absorbed by the PCL.¹⁸ The postero-lateral joint capsule, popliteus, medial collateral ligament, and posterior oblique ligament also helps to prevent posterior translation of tibia over femur.¹⁹

Management for grade I and II sprains where only a proportion of fibres are involved includes rehabilitation and non-steroidal anti-inflammatory drugs. Surgical treatment includes ligament reconstruction using either hamstring, peroneus or bone patellar tendon bone graft.^20–22

Objectives

The primary objective of the study is to assess the functional, clinical and radiological outcome of posterior cruciate ligament injuries managed surgically. The secondary objectives of the study are to study the aetiology of posterior cruciate ligament injuries, and to assess any complications associated with management modalities.

Registration

This trial has been registered with CTRI (REF/2023/06/068422).

Trial design

This is a single group type of trial with participants being surgically managed for PCL injuries. The framework of the trial is superiority and exploratory. This is a hospital-based experimental study.

Participants

The study will be conducted in Department of Orthopaedics, Jawaharlal Nehru Medical College (JNMC) and Acharya Vinoba Bhave Rural Hospital (AVBRH), Wardha, Maharashtra, India. Included in the study will be all skeletally matured patients of age 25 years and above, both male and female, with symptoms and traumatic PCL injuries planned for surgical management. Exclusion criteria will be patients with injuries to the PCL who will be managed conservatively, injuries to the PCL that have infectious foci, tumour conditions, osteoarthritic changes, and congenital and metabolic disorders.

Interventions

A pre-intervention assessment will be done, taking detailed clinical history with assessment pro-forma, clinical examination, and radiological tests such as X-ray and magnetic resonance imaging, as well as all routine examination like complete blood count, liver function tests, kidney function test, random blood sugar, chest X-ray, electrocardiogram and with functional parameters. Pre-anaesthetic check-up, part preparation and physician fitness will be obtained for each patient. Arthroscopic PCL reconstruction with double-bundle graft²³ surgery will be performed, and the expected duration of the surgery will be two to three hours. Patients will be arranged supine on the operating table. Under all aseptic precautions and antibiotic prophylaxis, the site to be operated on will be prepared thoroughly keeping the knee joint in flexion. A tourniquet applied around the proximal thigh will be inflated. Arthroscopic portals will be placed and a scope inserted to visualise the PCL tear. Regarding the type of graft used (auto-graft), if the patient has a PCL avulsion fracture then interference cc screw will be used; if they have a single PCL injury then a hamstring graft, i.e. semitendinosus and semimembranosus graft will be used, and if they have a multi ligament injury then a peroneus tertius graft will be used. Similar considerations will be given to the anaesthesia used: if the participant has an avulsion and single ligament injury then spinal anaesthesia will be given, and if they have a multi ligament injury then spinal and epidural anaesthesia will be given. Arthroscopic tunnels will be positioned with graft in place using endobutton loop and fixed with interference screw or suture disc. A thorough wash will be given, closure to be done in layers with sterile dressing in situ and long knee brace²¹ will be applied before moving the patient to the recovery ward for observation. Pre and intra-operative discontinuation or modifications will be considered as per the participant’s request and possible improvement or worsening of their condition. Post-intervention, all assessments will be repeated using clinical examination, pro-forma, radiological findings and with functional parameters. Post-operatively Mass General Brigham rehabilitation protocol for PCL reconstruction will be followed. Clinical, radiological and functional results of PCL injuries will help to investigate the causes and to evaluate any problems related to treatment options and any complications associated with it. The participants enrolled in the study will be followed up for post-operative assessment at intervals of 1 month, 3 months, 6 months and then 2 years.

Outcomes

Primary outcome measures

Figure 1. Lysholm knee scoring scale.

Figure 2. IKDC knee scoring system.

Secondary outcome measures

Sample size

The sample size formula (Daniel, 1999) is used,²⁶ which is

If the population is more than 10,000 where,

Z = statistic for a level of confidence. (For the level of confidence of 95%, which is conventional, Z value is 1.96).

P = expected prevalence or proportion i.e. prevalence of PCL injuries in India = 2.76% = 0.0276.²⁷

d = precision or desired error of margin = 7% = 0.07

Statistical methods: Student’s t-test, one way ANOVA and Pearson’s correlation coefficient.

Data collection, management and analysis

A total of 25 participants will be enrolled in the study who meet the inclusion criteria. All the participants will be educated about the purpose of the research, will then undergo the pre-study assessment and will complete clinical and radiological tests as described above. They will also undergo the Lysholm knee scoring scale and the IKDC knee scoring system, and the baseline data will be noted for each participant. The participants will be followed up for a minimum of 6 months and a maximum of 2 years from the treatment, as is suitable for the patient and the researcher. On every follow up, complications, if any, will be noted and managed appropriately. All the relevant statistical data will be collected pre, intra, and post-operatively along with follow up data which will be recorded for each of the outcome measures (Figure 3). The obtained data will then be tabulated in an Excel sheet and a master chart will be created, and later be used for statistical analysis. To carry out the statistical analysis, SPSS version 27 software will be used. The analysis will be done considering the desired error of margin and confidence interval of 95%.

Figure 3. Study design.

This protocol is addressed in accordance with SPIRIT reporting guidelines.²⁸

Dissemination

This study will be published in indexed journal.

Study status

Data collection has not yet started.

Ethical considerations

This research protocol received approval from the institutional ethical committee of the Datta Meghe Institute of Higher Education and Research (approval number ECR/440/Inst/MH/2013/RR-2019) on 18/07/2022.

All participants will be educated about the purpose of the research. Written and verbal informed consent will be obtained from all the participants by the principal investigator prior to the intervention. Procedures in this study will be conducted in accordance with the Helsinki Declaration of 1975, as referenced in 2008.

The study material will be considered to be confidential documents and will be safely stored with access only to the principal investigator.