• Hip and knee surgery

Improving treatment in patients scheduled for total knee arthroplasty. The role of preoperative low-load blood flow restricted resistance training.
Jørgensen SL

Background: The number of total knee arthroplasties (TKA) due to knee osteoarthritis (OA) increases worldwide. Despite being a successful surgery, ~20% of the patients perceive insufficient postoperative outcomes. Also, the majority of patients demonstrate long-lasting impairments in physical function following TKA compared with healthy peers. Improving preoperative knee extensor strength is proposed to enhance postoperative physical function. Low-load blood flow restricted resistance training (BFR-RT) increases skeletal strength and size and physical function with minimal stress on the knee joint.

Aims: The main aims of the overall PhD project were to
i. Outline the complete description of the trial protocol (Paper I)
ii. Evaluate the associations to lower limb sit-to-stand power (STS Power) or maximal isometric knee extensor strength (knee extensor MVC), respectively, with objective measures of physical function and patient-reported outcomes (Paper II).
iii. Determine if STS Power or knee extensor MVC would be differently related to physical function and patient-reported outcomes (Paper II)
iv. Investigate the efficacy of preoperative BFR-RT compared with usual preoperative medical care on physical function, lower limb strength, and patient-reported outcomes three months after TKA (Paper III & IV).

Methods: The intervention phase of the PhD project was designed as a randomized, controlled, assessor-blinded trial (RCT). Patients ≥50 years scheduled for TKA at Horsens- or Silkeborg Regional Hospital due to knee OA were randomly assigned to (i) eight weeks of preoperative BFR-RT or (ii) usual preoperative medical care. The primary endpoint was between-group mean change in 30-sec sit-to-stand (30STS) performance three months after TKA. Key secondary outcomes were: Timed Up & Go (TUG), 40-meter fast-paced walk test (40mFWT), 1 repetition maximum (RM) leg press and knee extensor strength, knee extensor and flexor MVC, the Knee Injury & Osteoarthritis Outcome Score (KOOS), and the EQ-5D-L5 questionnaire. Paper II was designed as a cross-sectional study comprising baseline data from all trial participants. Linear and multiple regression analyses and Pitman's test were applied with STS Power and knee extensor MVC as the dependent variables. The cohort was divided into a male- and female-patient cohort. Papers III and IV present intention-to-treat results from the RCT collected on the primary and secondary outcomes at baseline, pre-surgery, and three months after surgery.

Findings: At baseline, only STS Power was statistically associated with TUG and 40mFWT in our male- and female patient cohorts, and with KOOS subscales of Pain, Activities of Daily Living, and Sport & Recreational Activities in our male patient cohort (Study II). STS Power was equal or more strongly correlated to TUG, 40mFWT, and the KOOS subscales compared with the correlation coefficients derived with knee extensor MVC (Study II).
No significant between-group changes were observed in physical function or patient-reported outcomes from baseline to three months after surgery. Patients following usual preoperative medical care demonstrated significant postoperative decreases in leg extensor strength in the affected leg, while BFR-RT sustained preoperative levels of leg extensor strength (Paper III & IV).

Interpretation: STS Power can be used as a time-efficient and inexpensive measure to estimate ambulatory and walking speed in patients with advanced stages of knee OA (Study II).
The present preoperative BFR-RT protocol did not improve the postoperative measures of physical function or patient-reported outcomes compared with receiving usual preoperative medical care. The patients in the BFR-RT group only exercised the affected leg, which may, in part, explain the lack of significant between-group changes. However, preoperative BFR-RT protected against decreases in maximal knee extensor strength in the exercised leg (Paper III & IV).